Most dairy cattle are bred by artificial insemination. Frozen semen is used by top producers to inseminate 95% of cows and 89% of heifers. Semen is extended (diluted) and frozen until thawed for use for insemination. A single ejaculate from a good bull can be used to inseminate as many as 1,000 cows. Presently, sperm dilution is normally considered to be limited to a concentration of not less than 5 million motile sperm for a 1/2 ml insemination (not less than 10 million motile sperm per milliliter). This dilution provides a "non-return" rate of 70% if conditions are optimal. The non-return rate refers to the failure of cows to return to the estrous state and therefore is directly correlated with incidence of pregnancy. Typically, 10 to 30 million bull sperm are inseminated in a volume of 0.5 ml to obtain a non-return rate of 50 to about 75%. So even if artificial insemination is used to significantly increase the reproductive efficiency of valuable bulls, millions of sperm are still needed for insemination. It is of interest to the dairy industry to be able to improve the non-return rate or reduce the number of sperm required per insemination.
We turn now to some technical background from which the invention was conceived. It has been discovered that for cows sperm become trapped in the oviduct just beyond the entrance to the oviduct by sticking (binding) to the inner surface of the wall of the oviduct (referred to hereinafter sometimes as "oviductal epithelium"). This results in formation of a sperm reservoir. As the time of ovulation approaches, sperm are released from the reservoir to fertilize the egg. Capacitation is considered to change the sperm to cause said release. It has been found that the molecules on the oviductal epithelium provide certain sugar moieties which bind to molecules on sperm and that this causes the binding of sperm to oviductal epithelium and formation of a sperm reservoir thereon. Binding of sperm to oviductal epithelium and release therefrom may serve the functions of reducing or preventing polyspermic fertilization and of prolonging the life and fertility of sperm (i.e., maintaining sperm fertilizing capacity). Thus, the binding of sperm to oviductal epithelium to form a sperm reservoir is considered a beneficial occurrence and important to fertilization. Research is and has been carried out on how sperm transport is regulated by oviductal epithelium. Fucose has been detected on the oviductal epithelial surface and sperm binding is reduced when fucose is enzymatically removed from the epithelial surface, indicating that fucose is what sperm bind to when they enter the oviduct. Furthermore, it has been discovered that the application of fucose, polymerized fucose, and fucose linked in certain linkages in oligosaccharide, inhibits the binding of the sperm to oviductal epithelium presumably by competitive inhibition of binding, i.e., by binding to sperm so fucose in oviductal epithelium cannot bind to sperm.